ADVANCED FUNCTIONAL MATERIALS, Issue 6 2010
Sung-Min Yoon
Abstract A fully transparent non-volatile memory thin-film transistor (T-MTFT) is demonstrated. The gate stack is composed of organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and oxide semiconducting Al-Zn-Sn-O (AZTO) layers, in which thin Al2O3 is introduced between two layers. All the fabrication processes are performed below 200,°C on the glass substrate. The transmittance of the fabricated device was more than 90% at the wavelength of 550,nm. The memory window obtained in the T-MTFT was 7.5,V with a gate voltage sweep of ,10 to 10,V, and it was still 1.8,V even with a lower voltage sweep of ,6 to 6,V. The field-effect mobility, subthreshold swing, on/off ratio, and gate leakage currents were obtained to be 32.2,cm2 V,1 s,1, 0.45,V decade,1, 108, and 10,13 A, respectively. All these characteristics correspond to the best performances among all types of non-volatile memory transistors reported so far, although the programming speed and retention time should be more improved. [source]

Influence of Dielectric Surface Chemistry on the Microstructure and Carrier Mobility of an n-Type Organic Semiconductor

ADVANCED FUNCTIONAL MATERIALS, Issue 15 2009
Parul Dhagat
Abstract This paper examines the microstructure evolution of 3,4,9,10-perylene-tetracarboxylic bis-benzimidazole (PTCBI) thin films resulting from conditions imposed during film deposition. Modification of the silicon dioxide interface with a hydrophobic monolayer (octadecyltrichlorosilane (OTS-18)) alters the PTCBI growth habit by changing the unit cell contact plane. PTCBI films deposited on oxide surface have an orientation of (011), while films atop OTS-treated oxide surface have a preferred orientation of (001). The quality of the self assembled monolayer does not appear to influence the PTCBI growth preference significantly yet it enhances the carrier mobility, suggesting that charge traps are adequately passivated due to uniform monolayer coverage. High-quality monolayers result in n-type carrier mobility values of 0.05,cm2V,1s,1 Increasing the substrate temperature during PTCBI film deposition correlates with an increase in mobility that is most significant for films deposited on OTS-treated surface. [source]

A Densely and Uniformly Packed Organic Semiconductor Based on Annelated , -Trithiophenes for High-Performance Thin Film Transistors

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2009
Lin Tan
Abstract A novel semiconductor based on annelated , -trithiophenes is presented, possessing an extraordinary compressed packing mode combining edge-to-face ,,, interactions and S,S interactions in single crystals, which is favorable for more effective charge transporting. Accordingly, the device incorporating this semiconductor shows remarkably high charge carrier mobility, as high as 0.89,cm2,V,1,s,1, and an on/off ratio of 4.6,×,107 for vacuum-deposited thin films. [source]

Nucleation-Governed Reversible Self-Assembly of an Organic Semiconductor at Surfaces: Long-Range Mass Transport Forming Giant Functional Fibers,

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007
G. De, Luca
Abstract The use of solvent-vapor annealing (SVA) to form millimeter-long crystalline fibers, having a sub-micrometer cross section, on various solid substrates is described. Thin films of a perylene-bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer-sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re-organize into long fibers that have a remarkably high aspect ratio, exceeding 103. Time- and space-resolved mapping with optical microscopy allows the self-assembly mechanism to be unravelled; the mechanism is found to be a nucleation-governed growth, which complies with an Avrami-type of mechanism. SVA is found to lead to self-assembly featuring i),long-range order (up to the millimeter scale), ii),reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl3 as solvents, iii),remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self-assembled architectures with pre-programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron-accepting character than the smaller needles of the drop-cast films. The giant fibers can be grown in,situ in the gap between microscopic electrodes supported on SiOx, paving the way towards the application of SVA in micro- and nanoelectronics. [source]

Organic Electronics: High-mobility Ambipolar Transistors and High-gain Inverters from a Donor,Acceptor Copolymer Semiconductor (Adv. Mater.

ADVANCED MATERIALS, Issue 4 2010
4/2010)
The cover illustrates a polymer semiconductor highway for efficient transport of both electrons and holes. On p. 478, Samson A. Jenekhe, Mark D. Watson, and co-workers have demonstrated high-mobility single-component ambipolar field-effect transistors, by utilizing a new polymer semiconductor, and integrated them into complementary inverters. Polymer semiconductors with good ambipolar charge transport provide a simpler way to realize complementary circuits and other devices and functions in organic electronics. [source]

High-mobility Ambipolar Transistors and High-gain Inverters from a Donor,Acceptor Copolymer Semiconductor

ADVANCED MATERIALS, Issue 4 2010
Felix Sunjoo Kim
High-performance ambipolar transistors and inverters are demonstrated using a new donor,acceptor copolymer semiconductor. The ambipolar transistors show electron and hole mobilities of up to 0.04 and 0.003 cm2 V,1 s,1, respectively. Voltage transfer curves of the inverters made on common gold electrodes showed sharp switching with gain of 30. [source]

Efficient, Stable Bulk Charge Transport in Crystalline/Crystalline Semiconductor,Insulator Blends

ADVANCED MATERIALS, Issue 44 2009
Avinesh Kumar
Efficient and stable ambipolar charge transport in the bulk of crystalline/crystalline P3HT/HDPE systems, as evidenced by time-of-flight (TOF) photoconductivity measurements, is found. Interestingly, certain blend compositions displayed significantly enhanced bulk charge-transport properties compared to neat P3HT, with ,TOF measured for 80:20,wt% P3HT:PE blends being up to one order of magnitude higher than those found in neat P3HT. [source]

Electronic Manifestation of Cation-Vacancy-Induced Magnetic Moments in a Transparent Oxide Semiconductor: Anatase Nb:TiO2

ADVANCED MATERIALS, Issue 22 2009
Shixiong Zhang
Nb-doped anatase TiO2 thin films grown by pulsed-laser deposition show Kondo scattering in elctronic-transport measurements, providing evidence for the formation of magnetic moments. The origin of magnetism is attributed to cation (Ti) vacancies, confirmed by X-ray absorption spectroscopy and first-principle calculations. The Ti vacancies are controlled by oxygen partial pressure during growth. [source]

Organic Semiconductors: Relating the Functional Properties of an Organic Semiconductor to Molecular Structure by nc-AFM (Adv. Mater.

ADVANCED MATERIALS, Issue 20 2009
20/2009)
The influence of the molecular scale arrangement on the optoelectronic properties of organic semiconductors can be investigated using noncontact AFM to determine the local structure of molecular islands and probe the local optical excitation response of different molecular-scale structures, report Peter Grutter and co-workers on p. 2029. The cover image shows a 3D rendering of a high-resolution noncontact AFM image of a monolayer of PTCDA molecules trapped in a nanoscale pit in NaCl, one of the structures investigated, under "illumination". [source]

Relating the Functional Properties of an Organic Semiconductor to Molecular Structure by nc-AFM

ADVANCED MATERIALS, Issue 20 2009
Sarah A. Burke
The structure and properties of different molecular scale PTCDA arrangements are investigated by noncontact-AFM. A hybrid optical,electrostatic characterization is used to locally probe freely grown and nanoconfined structures in order to connect opto-electronic properties with the molecular scale structure determined by high resolution AFM. [source]

Dithieno[2,3- d;2,,3,- d,]benzo[1,2- b;4,5- b,]dithiophene (DTBDT) as Semiconductor for High-Performance, Solution-Processed Organic Field-Effect Transistors,

ADVANCED MATERIALS, Issue 2 2009
Peng Gao
The facile synthesis of a new five-ring-fused pentacene analog with four symmetrically fused thiophene ring units (Dithieno[2,3- d;2,,3,- d,]benzo[1,2- b;4,5- b,]dithiophene, Cn -DTBDT) is presented. After aligning this material from solution, thin films for organic field-effect transistors were obtained, resulting in excellent hole mobilities of up to 1.7 cm2V,1s,1, and on/off ratio of 107. [source]

High-Performance Field-Effect Transistor Based on Dibenzo[d,d,]thieno[3,2- b;4,5- b,]dithiophene, an Easily Synthesized Semiconductor with High Ionization Potential,

ADVANCED MATERIALS, Issue 19 2007
H. Gao
Three simple, controlled steps are all it takes to synthesize the title pentacene analogue DBTDT (see figure). The material's high ionization potential, high thermal and photostability, high mobilities, and an on/off ratio larger than 106 at a substrate temperature of ca.,36,°C, as reported here, suggest that DBTDT will be extremely valuable for applications in plastic organic electronics. [source]

Digital photography: A primer for pathologists

JOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 2 2004
Roger S. Riley
Abstract The computer and the digital camera provide a unique means for improving hematology education, research, and patient service. High quality photographic images of gross specimens can be rapidly and conveniently acquired with a high-resolution digital camera, and specialized digital cameras have been developed for photomicroscopy. Digital cameras utilize charge-coupled devices (CCD) or Complementary Metal Oxide Semiconductor (CMOS) image sensors to measure light energy and additional circuitry to convert the measured information into a digital signal. Since digital cameras do not utilize photographic film, images are immediately available for incorporation into web sites or digital publications, printing, transfer to other individuals by email, or other applications. Several excellent digital still cameras are now available for less than $2,500 that capture high quality images comprised of more than 6 megapixels. These images are essentially indistinguishable from conventional film images when viewed on a quality color monitor or printed on a quality color or black and white printer at sizes up to 11×14 inches. Several recent dedicated digital photomicroscopy cameras provide an ultrahigh quality image output of more than 12 megapixels and have low noise circuit designs permitting the direct capture of darkfield and fluorescence images. There are many applications of digital images of pathologic specimens. Since pathology is a visual science, the inclusion of quality digital images into lectures, teaching handouts, and electronic documents is essential. A few institutions have gone beyond the basic application of digital images to developing large electronic hematology atlases, animated, audio-enhanced learning experiences, multidisciplinary Internet conferences, and other innovative applications. Digital images of single microscopic fields (single frame images) are the most widely utilized in hematology education at this time, but single images of many adjacent microscopic fields can be stitched together to prepare "zoomable" panoramas that encompass a large part of a microscope slide and closely simulate observation through a real microscope. With further advances in computer speed and Internet streaming technology, the virtual microscope could easily replace the real microscope in pathology education. Later in this decade, interactive immersive computer experiences may completely revolutionize hematology education and make the conventional lecture and laboratory format obsolete. Patient care is enhanced by the transmission of digital images to other individuals for consultation and education, and by the inclusion of these images in patient care documents. In research laboratories, digital cameras are widely used to document experimental results and to obtain experimental data. J. Clin. Lab. Anal. 18:91,128, 2004. © 2004 Wiley-Liss, Inc. [source]

ta-C/Si heterojunction diodes with apparently giant ideality factors

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2010
Marc Brötzmann
Abstract A common feature of many wide band gap heterojunction diodes is an unexplained large ideality factor n > 2. In this context we investigate the diode characteristics of heterojunction diodes consisting of a crystalline semiconductor material such as Si covered with a thin semiconducting film of amorphous or disordered material. As thin amorphous film we use tetrahedral amorphous carbon (ta-C). These heterojunctions exhibit a pronounced rectifying behavior, low saturation current and low parasitic currents. Moreover, we observe an apparently giant ideality factor reaching values of n > 75. As a consequence, the turn on voltage is around 3 , 10 V and the I-V curves can be measured for bias up to 40 V without reaching saturation or electrical breakdown. We present a quantitative model for the unusual diode characteristics of these Metal , Amorphous Semiconductor , Semiconductor diodes (MASS-diodes). We demonstrate that the I-V characteristics of the heterojunctions are well described by a serial arrangement of an ideal Schottky-diode, a Frenkel-Poole type resistance and an Ohmic contact resistance, emulating a p-n- or Schottky diode characteristic with giant ideality factor and referred to as the FPID-model. We propose that heterojunctions exhibiting apparently large ideality factors n , 2 may possess an interfacial disordered or amorphous layer with Frenkel-Poole conduction properties. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Selective Pulsed Heating for the Synthesis of Semiconductor and Metal Submicrometer Spheres,

ANGEWANDTE CHEMIE, Issue 36 2010
Hongqiang Wang Dr.
Heiße Sache: Zur Synthese von Halbleiter- und Metallkügelchen muss das anisotrope Kristallwachstum eingedämmt werden, dies ist bei Anwendung herkömmlicher Heizmethoden aber schwer zu erreichen. Selektives Heizen von Nanopartikel-Kolloiden durch Laserpulse führt dagegen zu Halbleiter- und Metallkügelchen mit Submikrometergröße. [source]

Visible-Light-Induced Selective CO2 Reduction Utilizing a Ruthenium Complex Electrocatalyst Linked to a p-Type Nitrogen-Doped Ta2O5 Semiconductor,

ANGEWANDTE CHEMIE, Issue 30 2010
Shunsuke Sato Dr.
Licht, CO2, Action! Die selektive CO2 -Reduktion durch Hybridphotokatalysatoren aus einem p-Halbleiter und einem Rutheniumkatalysator (siehe Bild) wurde durch sichtbares Licht induziert. Die Quantenausbeute der HCOOH-Bildung betrug bei 405,nm 1.9,%. Damit Elektronentransfer stattfindet, muss das Potential des Leitungsbandminimums des Halbleiters negativer sein als das Reduktionspotential des Komplexkatalysators. [source]

Titelbild: A Crystal-Engineered Hydrogen-Bonded Octachloroperylene Diimide with a Twisted Core: An n-Channel Organic Semiconductor (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 4 2010
4/2010)
Molekül- und Kristall-Engineering lieferten leistungsstarke organische Dünnfilm-Transistoren (TFTs) auf der Grundlage eines sehr elektronenarmen Octachlorperylendiimids (Cl8 -PTCDI). F.,Würthner, Z. Bao et,al. beschreiben in der Zuschrift auf S.,752,ff. ein faszinierendes Kristall-Engineering-Konzept, das zweidimensionale Perkolationswege für den Elektronentransport erschließt und TFTs mit ausgezeichneten Mobilitäten und An-Aus-Stromverhältnissen unter Normalbedingungen liefert. [source]

A Crystal-Engineered Hydrogen-Bonded Octachloroperylene Diimide with a Twisted Core: An n-Channel Organic Semiconductor,

ANGEWANDTE CHEMIE, Issue 4 2010
Marcel Gsänger
Verdreht: Perchlorierung von Perylendiimid führt zu einem außergewöhnlich elektronenarmen organischen Halbleitermolekül (siehe Bild; C schwarz, Cl grün, O rot, N blau, H weiß), das in einer idealen Backsteinanordnung mit engen ,-,- und Chlor-Chlor-Kontakten kristallisiert. Aus der Gasphase abgeschiedene dünne Filme aus dieser Verbindung sind ausgezeichnete Transistoren, sogar an Luft (,,0.8,cm2,V,1,s,1, Ian/Iaus,108). [source]

ChemInform Abstract: A Low Band Gap Iron Sulfide Hybrid Semiconductor with Unique 2D [Fe16S20]8- Layer and Reduced Thermal Conductivity.

CHEMINFORM, Issue 22 2010
Min Wu
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Semiconductor,Metal Nanocomposites.

CHEMINFORM, Issue 22 2001
Photocatalysis of Gold-Capped TiO2 (TiO2/Gold) Nanoparticles., Photoinduced Fusion
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Fluctuating Rounds of Inward Investment in Peripheral Regions: Semiconductors in the North East of England

ECONOMIC GEOGRAPHY, Issue 1 2007
Stuart Dawley
Abstract: This article extends economic geography research on foreign direct investment episodes by developing a historically grounded understanding of the socio-institutional relations that shape and constrain different rounds of (dis)investment by multinational enterprises (MNEs) within a host region. Sensitive to the roles of contextuality, path dependency, and contingency, it argues that the temporal and spatial dynamics of volatile MNE (dis)investment are best tackled using a conceptual framework that accords a full and active role to the agency of the firm and its interrelations with the geographically variable socioinstitutional contexts that produce, regulate, and mediate investment decisions. The framework is used to interpret the brief but fluctuating history of the semiconductor fabrication industry in North Tyneside in the old industrial region of North East England. Within each investment episode, the empirical findings reveal the pivotal power and agency of the corporation in shaping and connecting processes across a variety of scales, places, and times. Contrasting corporate strategies illustrate the dynamic and contingent ways in which home and host national institutional contexts matter in mediating and regulating MNE investment decisions. [source]

Energy Level Alignment and Interactions at Potential Contacts for Spin Injection into Organic Semiconductors,

ADVANCED ENGINEERING MATERIALS, Issue 4 2009
Mandy Grobosch
The present study provides the interface electronic properties between La0.7Sr0.3MnO3 and two archetype organic semiconductors, CuPc and , -6T using a combined X-ray- and ultraviolet photoelectron spectroscopy. La0.7Sr0.3MnO3 is a ferromagnetic metal and can be used to inject spin-polarized current into organic semiconductors. The energy level alignment depends on the cleaning procedure that is applied to the La0.7Sr0.3MnO3 surface prior to deposition of the organic semiconductor. [source]

Back Cover: Fundamentals of Metal-induced Crystallization of Amorphous Semiconductors (Adv. Eng.

ADVANCED ENGINEERING MATERIALS, Issue 3 2009
Mater.
The Backcover shows a covering layer of aluminum lowers the crystallization temperature of amorphous silicon (a-Si). First the a-Si covers ("wets") the grain boundaries in the aluminum layer (Al). Once the wetting a-Si film has reached a critical thickness, crystallization starts at the grain boundaries. More details can be found in the article by E. J. Mittemeijer on page 131. [source]

Fundamentals of Metal-induced Crystallization of Amorphous Semiconductors

ADVANCED ENGINEERING MATERIALS, Issue 3 2009
Zumin Wang
Abstract A general, quantitative model has been developed that provides fundamental understanding of the metal-induced crystallization (MIC) of amorphous semiconductors. Interface thermodynamics has been shown to play a decisive role for the whether or not occurrence of MIC. The model has been employed to predict the MIC temperature for various metal/amorphous-semiconductor systems. A consequence of the model is the prediction that the thickness of an ultrathin, pure Al film put on the top of an amorphous Si layer can be used as a very accurate tool to tune the crystallization temperature of amorphous Si. These theoretical predictions have been confirmed experimentally. The fundamental understanding reached may lead to pronounced technological progress in the low-temperature manufacturing of crystalline-Si-based devices deposited on cheap and flexible substrates such as glasses, plastics, and possibly even papers. [source]

Fabrication of Sub-10,nm Metallic Lines of Low Line-Width Roughness by Hydrogen Reduction of Patterned Metal,Organic Materials,

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010
Mihaela Nedelcu
Abstract The fabrication of very narrow metal lines by the lift-off technique, especially below sub-10,nm, is challenging due to thinner resist requirements in order to achieve the lithographic resolution. At such small length scales, when the grain size becomes comparable with the line-width, the built-in stress in the metal film can cause a break to occur at a grain boundary. Moreover, the line-width roughness (LWR) from the patterned resist can result in deposited metal lines with a very high LWR, leading to an adverse change in device characteristics. Here a new approach that is not based on the lift-off technique but rather on low temperature hydrogen reduction of electron-beam patterned metal naphthenates is demonstrated. This not only enables the fabrication of sub-10,nm metal lines of good integrity, but also of low LWR, below the limit of 3.2,nm discussed in the International Technology Roadmap for Semiconductors. Using this method, sub-10,nm nickel wires are obtained by reducing patterned nickel naphthenate lines in a hydrogen-rich atmosphere at 500,°C for 1,h. The LWR (i.e., 3 ,LWR) of these nickel nanolines was found to be 2.9,nm. The technique is general and is likely to be suitable for fabrication of nanostructures of most commonly used metals (and their alloys), such as iron, cobalt, nickel, copper, tungsten, molybdenum, and so on, from their respective metal,organic compounds. [source]

Nanoscale Conducting Channels at the Surface of Organic Semiconductors Formed by Decoration of Molecular Steps with Self-Assembled Molecules

ADVANCED FUNCTIONAL MATERIALS, Issue 23 2009
Bumsu Lee
Abstract Under certain conditions, self-assembling molecules preferentially bind to molecular steps at the surface of crystalline organic semiconductors, inducing a strong local doping effect. This creates macroscopically long conducting paths of nanoscale width (a single crystalline analogue of organic nanowires) that can span distances of up to 1,cm between electrical contacts. The observed effect of molecular step decoration opens intriguing possibilities for visualization, passivation, and selective doping of surface and interfacial defects in organic electronic devices and provides a novel system for research on nanoscale charge transport in organic semiconductors. In addition, this effect sheds light on the microscopic origin of nucleation and growth of self-assembled monolayers at organic surfaces. It can also have implications in electronic patterning, nanoscale chemical sensors, integrated interconnects and charge-transfer interfaces in organic transistors and solar cells. [source]

Enhancement of Carrier Mobilities of Organic Semiconductors on Sol,Gel Dielectrics: Investigations of Molecular Organization and Interfacial Chemistry Effects

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2009
Tommy Cahyadi
Abstract The dielectric-semiconductor interfacial interactions critically influence the morphology and molecular ordering of the organic semiconductor molecules, and hence have a profound influence on mobility, threshold voltage, and other vital device characteristics of organic field-effect transistors. In this study, p-channel small molecule/polymer (evaporated pentacene and spin-coated poly(3,3,;-didodecylquarterthiophene) , PQT) and n-channel fullerene derivative ({6}-1-(3-(2-thienylethoxycarbonyl)-propyl)-{5}-1-phenyl-[5,6]-C61 , TEPP-C61) show a significant enhancement in device mobilities ranging from ,6 to ,45 times higher for all classes of semiconductors deposited on sol,gel silica gate-dielectric than on pristine/octyltrichlorosilane (OTS)-treated thermally grown silica. Atomic force microscopy, synchrotron X-ray diffraction, photoluminescence/absorption, and Raman spectroscopy studies provide comprehensive evidences that sol,gel silica dielectrics-induced enhancement in both p- and n-channel organic semiconductors is attributable to better molecular ordering/packing, and hence reduced charge trapping centers due to lesser structural defects at the dielectric-semiconductor interface. [source]

Modeling Electron and Hole Transport in Fluoroarene-Oligothiopene Semiconductors: Investigation of Geometric and Electronic Structure Properties,

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2008
E. Koh
Abstract A theoretical study using density functional theory is undertaken to gain insight into how the structural, electronic, and electron-transfer characteristics of three Fluoroarene-oligothiophene semiconductors influence the preferred transport of electrons versus holes in field-effect transistor applications. The intermolecular electronic coupling interactions are analyzed through both a simplified energy-splitting in dimer (ESID) model and as a function of the entire dimer Hamiltonian in order to understand the impact of site energy differences; our results indicate that these differences are generally negligible for the series and, hence, use of the ESID model is valid. In addition, we also investigate the reduction and oxidation processes to understand the magnitudes of the intramolecular reorganization energy for the charge-hopping process and expected barrier heights for electron and hole injection into these materials. From the electronic coupling and intramolecular reorganization energies, estimates of the nearest-neighbor electron-transfer hopping rate constant for electrons are obtained. The ionization energetics suggest favored electron injection for the system with perfluoroarene groups at the end of the thiophene core, in agreement with experiments. The combined analyses of the electron-transfer properties and ionization processes suggest possible ambipolar behavior for these materials under favorable device conditions. [source]

Cover Picture: Photolithographic Route to the Fabrication of Micro/Nanowires of III,V Semiconductors (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2005
Mater.
Abstract The cover shows a patterned assembly of GaAs nanowires with their ends tethered to a bulk single-crystal wafer as described on p.,30 by Rogers and co-workers. These wires, which have triangular cross-sections, were fabricated via a top,down process that combines photolithography and anisotropic chemical etching. Nano/microwires of semiconducting materials (e.g., GaAs and InP) with triangular cross-sections can be fabricated by "top,down" approaches that combine lithography of high-quality bulk wafers (using either traditional photolithography or phase-shift optical lithography) with anisotropic chemical etching. This method gives good control over the lateral dimensions, lengths, and morphologies of free-standing wires. The behaviors of many different resist layers and etching chemistries are presented. It is shown how wire arrays with highly ordered alignments can be transfer printed onto plastic substrates. This "top,down" approach provides a simple, effective, and versatile way of generating high-quality single-crystalline wires of various compound semiconductors. The resultant wires and wire arrays have potential applications in electronics, optics, optoelectronics, and sensing. [source]

Unprecedented Binary Semiconductors Based on TCNQ: Single-Crystal X-ray Studies and Physical Properties of Cu(TCNQX2) X=Cl, Br

ADVANCED MATERIALS, Issue 9 2010
Nazario Lopez
Single crystals of a new structure typefor the M+(TCNQ),, binary family are isolated from reactions of dihalogenated TCNQ derivatives and CuI ions (see figure; Cu: pink C: black, N: blue, Br: orange, H: light blue). The new compound Cu(TCNQCl2) exhibits the highest conductivity of the M+(TCNQ),, series to date, despite the larger separation of TCNQCl2 units in the stacks. Conductive properties of Cu(TCNQX2) where X,=,Cl, Br is attributed to charge-carrier transport through copper ions, which is unprecedented in M+(TCNQ),, materials. [source]